How do I hang a frameless mirror safely?

Every other wall fixing bolts through something. A frameless mirror gives you nothing to bolt through: the glass is the object, and glass does not tolerate point loads, drilling or twisting. So the whole job is about supporting it from underneath and restraining it at the top, and about accepting that this is a two-person operation.

Safety

What you'll need

• Mirror clips — J-clips, corner clips or a rail system
• Fixings matched to the wall type
• Stud detector and a cable and pipe detector
• Long spirit level and a pencil
• Gloves and eye protection
• A second person
• Mirror adhesive rated for mirrors specifically (optional)
• Soft packing or foam pads (optional)

Step by step

1. Weigh it, or work it out from the glass thickness.Mirror glass is about 2.5kg per square metre per millimetre of thickness. A 600 x 900mm mirror in 4mm glass is around 5.5kg; the same size in 6mm is over 8kg; a 1200 x 800mm in 6mm is around 14kg. This number decides everything that follows.
2. Establish the wall before choosing the method.Studs or masonry for anything above a few kilograms. On dot-and-dab, screws must reach the masonry behind the void. On plasterboard with no stud, fit a timber batten across two studs and mount the clips to that.
3. Scan for cables and pipes across the whole area.Mirrors go on bedroom, hall and bathroom walls, all of which carry cable runs — and bathroom walls carry pipes. Scan the full outline plus a margin, and stop if you are uncertain.
4. Fit the bottom clips first and let the mirror rest on them.Two J-clips or corner clips carrying the weight, set dead level. The mirror sits on these; they do the work. Get this line level and everything else follows.
5. Offer the mirror up with two people and mark the top.One person on each side, gloves on. Rest it on the bottom clips, check it stands upright and true, and mark where the top clips go.
6. Fit the top clips as restraint, not support.The top clips stop the mirror falling forward. Sliding top clips are the usual design: fitted loose, the mirror goes in, then they slide down over the edge and lock. They should touch the glass, not clamp it.
7. Never over-tighten anything against glass.A clip screwed down hard onto glass creates a point load and the mirror cracks, sometimes days later. Snug, with the soft washer or pad the clip came with in place.
8. Use adhesive only as a secondary fixing, and the right one.Mirror-specific adhesive only: ordinary solvent-based products attack the silvering from behind and produce black edges within months. Apply in vertical beads so any moisture can drain, keep it off the edges, and support the mirror mechanically while it cures. Adhesive alone is for small light mirrors on a rigid, sound, non-porous surface.
9. Pack behind the mirror if the wall is not flat.Foam pads or the spacers supplied with the clips. A large mirror pressed against a bulge in a wall is being bent, and bent glass breaks.
10. Check it and then leave it alone.Look along the edges for even contact, check nothing rocks, and give the adhesive its full cure time before removing any temporary support.

Tips

• Bathroom mirrors want a small ventilation gap behind them and adhesive applied in vertical beads, so trapped moisture can escape rather than sitting against the silvering.
• A mirror leaning against a wall — the large floor mirror look — is genuinely popular and completely safe only if it is strapped to the wall at the top. Unstrapped, a leaning mirror is a serious hazard around children.
• If a mirror needs holes for a fixing and it does not have them, a glass merchant will drill it. Never attempt to drill mirror glass with an ordinary drill bit.

Common mistakes

• Relying on adhesive alone for a large mirror — The bond is only as good as the wall surface, which is often paint over plaster. It fails progressively and then completely, and the mirror breaks into large pieces.
• Using ordinary construction adhesive or silicone — Solvents attack the silvering from the back. Black creeping patches appear within months and the mirror is ruined even if it stays on the wall.
• Fitting the top clips first — There is then nothing to rest the mirror on while you position it, and the bottom line ends up crooked. Bottom clips first, always.
• Tightening clips hard onto the glass — It puts a point load on the edge. Glass fails at point loads, and it often fails days later rather than at the moment of tightening.
• Hanging a mirror above a bed, a bath or a stairwell — Those are the three positions where a fall causes serious injury. Choose a different wall — mirrors work as well on any of them.

If it doesn't work

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